![Transcription Center logo](/themes/custom/tc_theme/assets/image/logo.png)
This transcription has been completed. Contact us with corrections.
209 4. [[underlined]]Monsieur Cassini's[[/underlined]] Answer was very kind, and disposed me to go to [[underlined]]Paris[[/underlined]] in [[underlined]]April[[/underlined]] 1682. But as he was prepossessed with the prevailing Opinion, That the Parallax of the Sun was very small; he concluded, in his Answer, that it could not be found by this Method. 5. I say then, at present, that the Sun's Parallax may be easily found, by means of the [[underline]]Arc[[/underline]] in the heavenly Sphere, [[underlined]]intercepted[[/underlined]] between the two apparent places of the Center of the Moon, when her Light seems terminated by a right Line, and when she comes to her apparent Quadrature. 6. Or else, in other equivalent Terms, I say, That the Sun's Parallax may be easily found, by means of the [[underlined]]Time intercepted[[/underlined]] between the [[underlined]]Two Moments[[/underlined]] when the Light of the Moon seems terminated by a right Line, and when she comes to her apparent Astronomical Quadrature. 7. When ye Section or Limit ye divides ye dark Part of the Moon from her inlightened Part appears as a right Line, then, the Line drawn from S the Center of the Sun, to [[L]] the Center of the Moon, is perpendicular to the Plane of that Section. And the Observator's Place being called O, the Measure of the Parallactic Angle LSO depends on the Distance betwixt the Centers of the Sun and of the Moon; or (which comes to the same) on the Distance betwixt the Center of the Sun and the Observator. 8. If the Sun's parallax be only of 10"30"' or of 9", as Sir [[underlined]]Isaac Newton[[/underlined]] did sometimes suppose: And if we reckon the apparent Semidiameter of the Sun to be of 16'10": Then, the Semidiameter of the Moon apparent to the Sun would result to Sir [[underlined]]Isaac Newton[[/underlined]] of 2"24. And this being substracted from 16'10"; there would remain 16'7",26 for the Breadth of the Zone [[end of page]]